1. Field of the Invention
The field of the present invention relates to a method for the reconstruction of a body map. Embodiments of the present invention can be applied to special advantage but not exclusively in the fields of medical imaging, non-destructive X-ray controls and, more particularly, medical diagnostic apparatuses. The field of the invention also relates to an X-ray apparatus comprising a method of this kind for the reconstruction of a body map.
2. Discussion of Related Art
X-ray diagnostic apparatuses are X-ray image acquisition apparatuses. These apparatuses are used to obtain images, or even sequences or images, of an organ situated inside a living being, especially a human being. An example of an X-ray apparatus such as this is shown in FIG. 1.
The X-ray apparatus of FIG. 1 has moving parts that enable it to rotate in different directions about a patient. These moving parts are capable of moving in all three dimensions of a space. These moving parts generally consist of a C-arm comprising an X-ray tube at one end and a detector at the other end. This tube enables an X-ray beam to be emitted along one direction of emission.
The detector 4 is hooked to the C-arm 2 opposite the tube 3 and in the direction of emission. The detector 4 is connected to a lift device used to raise and lower said detector in the direction of emission.
The C-arm is connected to a post 6 by means of a rotating arm 7 rotating about an axis 11 passing through an isocenter 12 of the X-ray apparatus. The post 6 rotates about an axis 13 passing through the isocenter 12 of the X-ray apparatus.
The X-ray apparatus also has an examination table 8, or a bed, on which a patient 9 reclines. This examination table 8 is placed within the C-arm 2 so that the tube 3 is beneath the examination table and so that the detector 4 is above the examination table.
All three elements, namely the post 6, the rotating arm 7 and the C-arm 2 are hinged relative to one another. This hinging of the post 6, the rotating arm 7 and the C-arm 2 enables the X-ray apparatus 1 to move in three dimensions. This motion of the moving parts of the X-ray apparatus 1 in three dimensions makes it possible to take several images of the organ to be examined at different angles of incidence.
In a radiology examination, the practitioner moves the C-arm 2 and/or the post 6 and/or the rotating arm 7 about the patient 9, especially around the part of the patient's body to be examined. To obtain better quality images, the lift device 5 with the detector 4 is lowered toward the patient. While this lift device is being lowered toward the patient 9, there is a risk that the detector 4 might collide with the patient 9.
To prevent risks of collision with the patient, prior X-ray apparatuses had a model of a virtual volumetric body of a virtual patient in a data base. This model of the virtual patient comprises fixed and simple shapes. The X-ray apparatus also has a model of the different elements of the X-ray apparatus in the data base.
The model of the X-ray apparatus combined with the model of the virtual patient is aimed at slowing down the motion of the moving parts of the X-ray apparatus in the event of a detection of proximity of the virtual patient's body or in the event of contact of one of the elements of the X-ray apparatus with the virtual patient's body. The contact between the model of the X-ray apparatus and the virtual patient does not stop the apparatus but simply slows it down. An anti-collision system 10 therefore has to be associated with the combination of the model of the X-ray apparatus and the model of the virtual patient's body. This anti-collision system 10 may be a proximity detector and/or a contact detector. This anti-collision system stops the motion of the moving parts of the apparatus in the event of contact with the real patient.
However, these prior X-ray apparatuses have drawbacks. During a radiology examination, when the patient's morphology is not the same as the morphology of the virtual patient, there is a very great risk of collision between the detector and the patient.
When the patient's size is smaller than that of the virtual patient, then the slowing down of the motion of the moving parts and the projection of the x-rays are done at a remote distance from the real patient. In this case, the detector is not close enough to the patient to give a high-quality image of the body part undergoing radiography, with a low dose of x-rays.
When the patient's size is greater than that of the virtual patient, then the moving parts get slowed down or stopped when it is too late to prevent collision between the detector and the patient.
With this anti-collision system, the practitioner has to manually reduce the speeds of the C-arm and/or the post and/or the rotating arm in order to reduce the risk of collision between the detector and those parts of the patient that are situated between the detector and the patient when these moving parts are at maximum speed and when the real patient's morphology is greater than that of the virtual patient. The practitioner also has to bring the detector manually closer to the real patient when this real patient's morphology is smaller than that of the virtual patient.
When the moving parts are at maximum speed, the practitioner is constantly afraid of injuring the patient. As a result, the practitioner is under a certain degree of pressure when these moving parts are moving. The practitioner then tends to reduce the speed of the moving parts, even when there is no risk of injuring the patient. This leads to lower productivity in the X-ray machine.
The use of this type of X-ray apparatus is essentially linked to action by the practitioner to control the speeds of the moving parts of the X-ray apparatus. The speed of the moving parts is therefore never at its maximum.
Furthermore the practitioner, who may be a doctor or a nurse or any person likely to use these apparatuses, must be trained to handle the speeds of the moving parts of the X-ray apparatus.